This invention relates to a method to produce tear reinforcement and seal line or tape for packaging essentially comprised of a fibrous yarn and a coating thereon of hot-melt adhesive which is compacted before solidification of the adhesive and formed after solidification into a desired final shape for use as a reinforcing tape or line in a packaging container as well as a package-opening device.
While not so limited, the present invention is particularly useful for producing a strand-like tape for use as a package seal or reinforcement element and/or, if desired, a tear element for opening a packaging container. Corrugated cartons used for packaging are cumbersome to reinforce from the standpoint of both expense and effectiveness. Stressed areas in a corrugated carton are usually reinforced by using heavy liners or multi-wall construction. Not only are the stressed areas reinforced but also the entire carton. However, unnecessary bulk and weight are added to the container. Such measures for reinforcing stressed areas of a carton also increase the coat without significant improvement to wet strength, bulge resistance, durability and loading strength.
To overcome these shortcomings and disadvantages, the present invention provides a method for producing a tape or line for packaging which dispenses with the need for expensive paper stock by utilizing high tensile strength filaments and hot-melt adhesive readily useful to add reinforcement to a corrugated container or the like either during the manufacturing process for the container or after manufacturing by the simple addition of heat to activate the thermoplastic adhesive for bonding the tape or line at the desired site. In this way, reinforcement is readily achieved at critical stress points to adapt the carton for specific needs. Moreover, package seal line is easily added and the same line may be used as reinforcement to absorb and spread compressive loads, shocks and stresses to enable the use of lower-weight liners without reducing the performance of the carton.
The coating method of the present invention is characterized by a high production capacity and capability or producing tear tape and/or seal and tear line essentially comprised of a compacted and shaped adhesive coating tightly adhered to fibrous yarn. Because of the nature of the product, fibrous yarn must be fed through a coating line at an economically feasible speed. However, the speed at which the coating process is carried out is dependent on variables including the type of yarn, material of the yarn and properties of the selected adhesive. The present invention is based on the discovery that the yarn must be preconditioned with respect to tension and cross-sectional shape immediately before coating with adhesive and within the very short residence time of the yarn in a bath of hot-melt adhesive. Absent such preconditioning of the yarn, there is an immediate stripping of any adhered coating in the bath because of the speed at which the yarn is pulled through the bath.